The aerodynamics of mountain bicycles: the role of computational fluid dynamics

The importance of aerodynamics in cycling has been recognised by both cyclists and engineers for many years. There is an abundance of published literature focusing on the development of more aerodynamically efficient rider positions, racing frames and components. Additionally the majority of the studies have been performed in wind tunnels, at velodromes and using coast down testing. This study shows that computational fluid dynamics (CFD) techniques, with its capability for testing a wide range of geometries at a relatively low cost, may be used to complement these experiments. The aerodynamics of cycling was studied using CFD, focusing on the aerodynamics of mountain bikes. The geometry of the bike and rider were created using CAD software and a 3D non-contact laser scanner, which captures up to 7500 points per second with an accuracy of up to 0.05mm. The computational mesh of 4,179,212 cells was created using Gambit and Tgrid. The simulations were run on Fluent version 6. The results of the study highlight the features of the mountain bike and rider caused by the rider. By analysing all the forces on the bike it was found that the rolling resistance equalled the aerodynamic drag at 8.75 ms-1, at faster speeds the aerodynamic drag was dominant.